Vacuum seal for wire feed



Sept 14, 1965 G. A. sHr-:PARD r-:TAL 3,206,217

VACUUM SEAL FOR WIRE FEED Filed NOV. 7. 1961 g wm.

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United States Patent O 3,206,217 VACUUM SEAL FOR WIRE FEED George A. IShepard, 6019 Charles Ave., Parma, Ohio;

Carl F. Brooker, Jr., 5357 E. 131st St., Garfield Heights 25, Ohio; and Joseph Cutrona, 216 E. Ridgewood Drive, Seven Hills 31, Ohio Filed Nov. 7, 1961, Ser. No. 150,723 3 Claims. (Cl. 277--60) This invention relates to a vacuum seal for a moving wire or the like and is particularly directed to a device for permitting wire to be passed continuously between a region of high pressure and a region of low pressure, including means for making sealed contact with the wire at all times, so as to prevent leakage of air or other gas between the high and low pressure region. In a special and important sense, the device is designed to provide a seal through which aluminum wire may be continuously fed from an outside supply into a high vacuum chamber.

An important use of the described vacuum seal is in metalizing apparatus, where a coating or plating of metal, such as aluminum, is deposited on desired Work or other substrate by vaporization of such aluminum in a vacuum chamber. The aluminum can be conveniently supplied to the vapor source, where it is heated and evaporated, by feeding the metal in the form of wire, but problems have been encountered in the provision of sealing structure at the point of entry of the aluminum into the chamber from a coil or other supply outside. Not only is it difficult to make full contact with a wire or equivalent rod-like element as such element moves axi-ally, but any abrasion or scratching of the aluminum by the sealing means produces imperfections in the surface of the wire, which in turn, even as they are formed, permit minor but objectionable leakage of air. This effect, i.e. scoring of the wire, is a special problem for wire of aluminum, since the `latter may be a relatively soft metal if used in a pure or nearly pure state as may be most suitable for vacuum metalizing. On the other hand, if the wire carries any burrs, slivers or the like, however minute, there may be unduly rapid wear of some types of sealing means such as surfaces of elastic material.

It may further be explained that for sealing purposes the wire-admitting device cannot make use of liquids or volatile substances, or indeed anything which might be carried with the wire into the enclosed space, either directly or in gasous form. The requirements of vacuum metalizing are particularly severe, since any foreign materials are highly undesirable, especially active gases such as atmospheric oxygen or water vapor, and the extremely low pressure used (of the order of l micron of mercury or more usually not more than about 1/2 micron) aggravates any problems of leakage or evaporation.

Accordingly, an important object of the invention is to provide an improved vacuum seal of the character described, which will allow rapid traversal of aluminum wire or the like and which will maintain sealed engagement with the wire and thus prevent appreciable leakage, over long periods of use. A further object is to afford novel devices of the nature stated, i.e., to seal the entrance of a moving wire into a vacuum chamber or the like, wherein the structure is mechanically simple, easy to disassemble for replacement of sealing elements, and readily adaptable to a variety of situations of use.

To these and other ends, the improved wire-sealing apparatus comprises a body structure, conveniently of elongated form, having a central passage therethrough which is shaped to be traversed by the wire in close but sliding t. The body structure is advantageously sectionalized, for ease of assembly with the sealing elements or for ease of replacement of the latter if necessary. The sealing elements comprise a plurality of cooperating 3,206,217 Patented Sept. 14, 1965 ICC devices, i.e., which serve jointly to constitute a highly useful seal, these elements being disposed within the body structure and in engaging relation with the wire.

One of the sealing means comprises one or more annular, toroidally curved bands or layers of elastically flexible material, which when in place are distorted or flexed into a sweeping or wiping contact with the wire. Specifically, this first sealing means may be constituted by one or more (preferably two) O-rings which are embedded, so to speak, in the interior surface of the body structure, i.e., surrounding the opening through which the wire passes, the arrangement being also conveniently such that the O-rings provide the seal between two sections or parts of the structure, which hold the rings in place.

In cooperation with the O-ring seal, the apparatus also includes a tapered, packed, compression-type seal, for example utilizing a layer of packing material intermediate tapered surfaces concentric with the passage through the body and arranged to be compacted against the aluminum wire surface. The packing material may be of various compositions, such as a body of at least somewhat deformable graphited fibrous packing, or heavily graphited, compressible plastic substances. As explained, this packing is disposed between mating parts, conveniently of conical configuration, whereby the packing layer is compressed into sealing engagement with the traveling wire, and also provides a seal between the parts. An additional, specific feature of the invention, which is greatly preferred, is that the body structure is fashioned from a synthetic resin (i.e., plastic) composition, particularly satisfactory results being achieved by making the body of nylon.

One form of the invention is illustrated in the accompanying drawings, by way of example, wherein:

FIG. l is a side view of the assembled vacuum seal device, schematically shown in association with a wall of a vacuum chamber into which wire must be fed;

FIG. 2 is a vertical section, through the center of the device, in a plane parallel to the plane of the drawing of FIG. l;

FIG. 3 is an exploded, perspective view, showing most of the parts of the device; and

FIG. 4 is a like exploded, perspective view, taken from an opposite direction, showing one of the packingengaging elements and the associated structure or layer of packing.

In general, the seal 10 comprises an elongated cylinder through which the aluminum wire 12 passes in a correspondingly elongated opening at the center, i.e., the axis of the assembly. As shown, the body of the device is formed of three parts 13, 14 and 15, arranged to be disposed in an endwise connected relation and held by four bolts 16, which traverse circumferentally spaced openings in the parts 14 and 15 and are threaded into correspondingly situated openings 18 in the element 13.

The passage 19 for the wire in the cylindrical part 13 is counterbored from one end to provide a cylindrical socket 20. The member 14 has a corresponding cylindrical projection 21 extending from one end thereof and adapted to be received, with relatively snug fit, by the opening 20 of the part 13. A space is provi-ded between the end of the projection 21 and the bottom of the cavity, so that one or more O-rings or equivalent, elastic, toroidally curved elements or bands can be disposed lat the inner end of the cavity and flexed into resilient, radial engagement with the passing wire. For instance, a pair of O- rings 23, 24 (which may be initially dimensioned for close lit with the wire) have been found particularly suitable, their dimensions and situation being such that when the assembly is tightened together the O-Iings are at least slightly deformed or iiattened to insure that the diameter of their central opening is somewhat less than the wire diameter, whereupon the passing wire further fiexes or deforms them by pressure radially outward of the opening and affords snug and complete engagement between the rings and the wire.

The part 14 at its opposite end is counterboarde to provide a conical recess 26, coaxial with the wire and disposed to cooperate with a correspondingly conical projection 28, of like slope, at one end face of the element 15, the projection 23 being axially shorter than the recess 26 to provide space for packing between the end of the projection and the bottom of the recess. A body 30 of packing, conveniently provided by winding graphited string or the like in the space between the frusto-conical projection and the frusto-conical recess, and thus assuming the shape of a hollow cone or frustum of a cone, is arranged to have its outer and inner surfaces respectively congruent, so to speak, with the tapered hole 26 in the member 14 and the tapered projection 28 of the adjacent end face of the member 15. Thus as will be clear from FIG. 4, the compacted winding of heavily graphited string can be conceived as forming a hollow conical body of packing (although not in fact put together as a separate piece, in the first instance), having a narrow inward flange portion 32 (with a central hole) to be squeezed against the wire, and is compressed into snug engagement or seating over the projection or nose 23 and against the interior of the recess 26.

All three of the parts 13, 14 and 15 are traversed by narrow central passages 19, 33 and 34 respectively, the passages being aligned in the assembled condition of the parts and being dimensioned for moderately close fit of the Wire, e.g. with a clearance from the latter of not more than about five to ten thousandths of an inch (0.005" to 0.010").

The end of the body member 13 opposite its face 35 which abuts the mating face 36 of the member 14, is provided with suitable means for attachment in or to the wall of the vacuum chamber. For example, the exterior of the member 13 is shown threaded at 38, so that it can be screwed into a flanged bushing or fitting indicated at 39 in the wall 40 of the chamber. This structure 39, 40 may also be arranged to carry, inside the chamber, appropriate mechanism such as coacting rollers (not shown) for drawing the wire continuously through the seal device 10.

It will now be seen that the parts are assembled by first disposing the O-rings, which are hollow, toroidal rings of rubber or similar, stiff elastic material, in the bottom of the cylindrical opening 20. The wire is passed through the openings 19, 33 and 34 of the respective members 13, 14 and 15, and the latter are then loosely assembled. That is, the member 14 is fitted to the member 13, with the cylindrical projection 21 inserted in the cavity so that the end of the projection abuts the stack of O-rings, that are now traversed by the wire. The packing is wound around the wire and over the surface of the conical nose 28, and the latter is pushed into the conical cavity of the member 14, so that the space between these parts, at the bottom around the wire, and between the tapered walls, is sufiiciently filled with pack- .ing to provide the desired seal.

Upon previously or now inserting, and upon now tightening the bolts 16 which traverse the entire assembly from the outer end of the member 15, through the part 14 and into the threaded apertures 18 of the element 13, the device is completed. The O-rings are compressed and deformed, causing their toroidally curved inner surfaces or layers to be squeezed against the wire when it traverses the central passage. At the same time, the packing 30 being a compressible material, yields somewhat, but with sufficiently maintained resilience, under the relatively heavy compression effectuated by the bolts 16. The inner ange of the packing is thus compressed firmly and snugly against the wire. As will be noted, the sealing arrangements constituted by the O-rings 23, 24 and the packing 30 not only engage the wire but also provide sealed contact between the several parts 13, 14 and 15. With the device mounted in a wall or like portion of a vacuum chamber, as indicated in FIG. 1, wire 12 may be continuously drawn through the assembly, i.e., through the passage 19-33-34, and may thus move into the vacuum region 42 from the air or atmospheric pressure region 43, while eifective sealing contact is achieved at all times to prevent leakage. It will be understood that once the device has been tightly assembled and installed, the tapered or pointed end of the wire of a new supply coil or reel can be readily fed through without disrupting the packing or sealing parts.

The device is adapted to accommodate a variety of sizes of metal Wire, as by appropriate dimensioning of the structure and the seals to suit the selected wire size. While for many purposes of metalizing, wires in the approximate range of one-sixteenth to one-half inch diameter are very effectively handled, the structure can be adapted to transfer larger wire or rod. The combination of sealing means may, however, be somewhat less tolerant to kinks and imperfections in wire of diameter larger than about one-half inch, but if the wire is of high uniformity, such tolerance raises no problem. As intimated, rods properly joined together are contemplated as an alternative form of metal feed which may be passed through the seal satisfactorily, the term wire being thus understood, unless otherwise specified, to include relatively rigid rod.

The packing 30 between the part 28 and recess 26 is, as explained, a suitably impregnated mass or assembly of flexible fibrous material, such as graphite impregnated string. T he impregnating substance may be any material that has very low vapor pressure, and a great degree of lubricity, and will not harden or set during use, examples being graphite, so-called high-vacuum greases, and the like. The string or other fibrous body can be a soft resilient fibrous material that will retain the impregnating substance and can be appropriately compacted to serve the stated function. Thus among `other things, suitable materials are cotton string, cotton batting, and like strings or bodies of asbestos fibers, wool fibers or plastic fibers.

The described different types of sealing means con stituted respectively by the O-rings 23-24 and the packing 30 cooperate in an unusual way to provide an effective but long-lasting high vacuum seal (down to pressures of the order of 0.1 micron or less) for the continuous advance of wire. While O-rings themselves are unusually effective, because of their great elasticity, in affording a very tight Seal on the wire, serious problems of wear were encountered when attempt was made to employ axially spaced sets of O-rings. Both sets showed considerable wear, the deterioration being very rapid for the forward ring or rings, i.e. those traversed first by the wire. In contrast, the present combination of seals, utilizing the conical, impregnated, fibrous packing at the forward or first-encountered station, has shown unexpectedly superior results in providing an effective seal, with relatively long life. In particular, it was found that in this arrangement the O-rings 23-24 at the second locality show greatly decreased wear (as compared with their behavior when O-rings were also used at the first locality), while the conical packing has a self-replenishing character, so to speak, which correspondingly obviates problems of wear at its locality.

It is believed that this coaction between the seals (employed for wire which is fed in the direction shown, by suitable means) is at least in part occasioned by the smaller degree of elasticity, i.e. the relative rigidity, in the conical packing. Such rigidity apparently causes the wire to be wiped clean of burrs and slivers, and also has a straightening action, i.e., eifectuates feed of the wire in a straightened path through the O-rings, all with the effect of reducing wear on the O-rings. The packing seal 30, as stated, has the ability, because fof its compressibility, .to replenish itself when it becomes worn or moved out of place by the wire, such replenishment being aided, if necessary, by slightly screwing down the bolts 16. While the O-rings are not self-replenishing, their wear has been essentially obviated in the manner described above, and at the same time, they effect a tighter vseal on the wire because of their great elasticity. The two seals also work in close conjunction at all times, in that when one of them is slightly opened, so to speak, to permit variations or kinks in the wire to pass through, the other is usually engaging a smooth, uniform portion of wire and thus maintains the required sealing function.

A further, specific feature of the invention is that the elements 13, 14 and 15 are made of nylon or similar essentially rigid plastic, e.g. synthetic resin material. While in some cases metal, such as brass, can be employed, the use of resin has been found to avoid all scoring or similar abrasion of the wire, with corresponding avoidance of even minute leakage of air. A still further advantage with nylon or similar plastics is that the coefficient of friction is relatively low so that the wire slides through the axial hole with relative freedom except for the close wiping or sweeping engagement of the O- rings 23, 24 and the similar squeezing engagement of the packing 30'.

As stated, the device has been found to be remarkably long lasting and reliable in that it has provided long periods of use, and indeed essentially indefinite use, for the feed of aluminum wire into a vacuum metalizing chamber, without deterioration of the sealing means.

It is to be understood that the invention is not limited to the specic embodiments herein described, but may be carried out in other ways without departure from its spirit.

We claim:

1. Apparatus for sealed contact with a longitudinally moving wire, comprising body structure having an elongated axial passage for traversal by the wire with close clearance and comprising nylon plastic material for avoiding abrasion of the wire, said body structure comprising first, second and third axially successive parts, one of said first and second parts having an axial recess and the other of said first and second parts having an axial projection arranged to enter said recess with a close circumferential fit, said first and second parts having mutually abutting faces adjacent the recess and projection, and lsaid recess and projection being shaped to provide a cavity, opening around the passage, between their respective bottom and end, two O-rings of elastic material having identical outer and opening diameters, arranged in said cavity in mutual abutment concentrically with the passage for sealing engagement with a wire traversing the passage and with the bottom of `the recess and end of the projection, one of said second `and third parts having a conical axial recess and the other of said second and third parts having a conical axial projection arranged to enter the conical recess, a cone-shaped layer of graphited, flexible fibrous packing material which is arranged to fit and be compressed between said conical recess and conical projection and which has an apex opening concentric with the passage and providing an inner edge of the layer to be forced against the traversing wire, and means for clamping said three parts together to hold the first and second parts in abutment with the O-rings embracing the wire and to compress the packing material between the second and third parts for sealing engagement of its inner edge with the wire and where said parts are so ordered that the wire passes through said fibrous packing before passing through said O-rings.

2. Apparatus for sealed contact with a longitudinally moving wire comprising:

body structure of essentially rigid plastic having an elongated passage for the wire;

a plurality of sealing O-rings -of elastic material having identical diameters of openings disposed for contact, under flexure, with the wire and arranged in mutual abutment concentrically with the passage at one locality;

a conical flexible, fibrous packing material, concentric with the passage and having an opening dimensioned to embrace the wire, positioned at another locality separate from said O-rings such that the wire passes through said fibrous packing before passing through said O-rings; and

means positioned on said body structure for compressing said fibrous packing inwardly against the wire and for forcing said O-rings radially inwardly against the wire.

3. Apparatus as defined in claim 2 wherein said body structure is formed of nylon plastic.

References Cited by the Examiner UNITED STATES PATENTS 134,955 l/73 Welch 277-115 884,864 4/08 Salt et al. 277-60 1,927,477 9/ 33 Walton 277-227 X 2,964,342 12/60 Mainprize 277-181 3,047,298 7/62 St. Clair et al 277-115 X 3,054,618 9/62 Abrams et al. 277-32 LEWIS I. LENNY, Primary Examiner.

SAMUEL ROTHBERG, EDWARD V. BENHAM,

Examiners. 

1. APPARATUS FOR SEALED CONTACT WITH A LONGITUDINALLY MOVING WIRE, COMPRISING BODY STRUCTURE HAVING AN ELONGATED AXIAL PASSAGE FOR TRAVERSAL BY THE WIRE WITH COSE CLEARANCE AND COMPRISIN NYLON PLASTIC MATERIAL FOR AVOIDING ABRASION OF THE WIRE, SAID BODY STRUCTURE COMPRISING FIRST, SECOND AND THIRD AXIALLY SUCCESSIVE PARTS, ONE OF SAID FIRST AND SECOND PARTS HAVING AN AXIAL RECESS AND THE OTHER OF SAID FIRST AND SECOND PARTS HAVING AN AXIAL PROJECTION ARRANGED TO ENTER SAID RECESS WITH A CLOSE CIRCUMFERENTIAL FIT, SAID FIRST AND SECOND PARTS HAVING MUTUALLY ABUTTING FACES ADJACENT THE RECESS AND PROJECTION, AND SAID RECESS AND PROJECTION BEING SHAPED TO PROVIDE A CAVITY, OPENING AROUND THE PASSAGE, BETWEEN THEIR RESPECTIVE BOTTOM AND END, TWO O-RINGS OF ELASTIC MATERIAL HAVING IDENTICAL OUTER AND OPENING DIAMETERS, ARRANGED IN SAID CAVITY IN MUTUAL ABUTMENT CONCENTRICALLY WITH THE PASSAGE FOR SEALING ENGAGEMENT WITH A WIRE TRAVERSING THE PASSAGE AND WITH THE BOTTOM OF THE RECESS AND END OF THE PROJECTION ONE OF SAID SECOND AND THIRD PARTS HAVING A CONICAL AXIAL RECESS AND THE OTHER OF SAID SECOND AND THIRD PARTS HAVING A CONICAL AXIAL PROJECTION ARRANGED TO ENTER THE CONICAL RECESS, A CONE-SHAPED LAYER OF GRAPHITED, FLEXIBLE FIBROUS PACKING MATERIAL WHICH IS ARRANGED TO FIT AND BE COMPRESSED BETWEEN SAID CONICAL RECESS AND CONICAL PROJECTION AND WHICH HAS AN APEX OPENING CONCENTRIC WITH THE PASSAGE AND PROVIDING AN INNER EDGE OF THE LAYER TO BE FORCED AGAINST THE TRAVERSING WIRE, AND MEANS FOR CLAMPING SAID THREEPARTS TOGETHER TO HOLD THE FIRST AND SECOND PARTS IN ABUTMENT WITH THE O-RINGS EMBRACING THE WIRE AND TO COMPRESS THE PACKING MATERIAL BETWEEN THE SECOND AND THIRD PART FOR SEALING ENGAGEMENT OF ITS INNER EDGE WITH THE WIRE AND WHERE SAID PARTS ARE SO ORDERED THAT THE WIRE PASSES THROUGH SAID FIBROUS PACKING BEFORE PASSING THROUGH SAID O-RINGS. 